Propeller slipstream enhancer

ABSTRACT

The invention relates a fluid or air propeller propulsion apparatus using modified state of the art propeller that reduces the typical propeller slipstream disc contraction at the propeller tips, by simply adding a novel channel or trough on the back surface spanwise midway between the leading edge and trailing edge. A portion of the air or fluid flowing over the back face of propeller blade is raked off and collected in the channel during rotation of the propeller, wherein the fluid or air is acted upon by centrifugal force varying directly with the propeller speed causing the fluid or air to be accelerated thru the channel or trough to the trailing edge of the propeller. This additional flow increases the propeller capacity additional jetting action bootstrapping causing the propeller to turn more easily, all of which increases the propeller thrust and efficiency as much as 10 percent.

BACKGROUND OF THE INVENTION

Enhancing the efficiency of axial flow propellers has long been a goal of inventors, scientists, researchers, and manufacturers. It is well known the propeller slipstream disc contraction occurs near the outer edge of the propeller disc between 0.816 to 0.920 depending on the propeller forward velocity from zero and low forward speed. Static Propellers & Helicopter Rotors, AHS 25^(th) Forum 1969, and Fluid-Dynamic Lift, Chapter XII, S. F. Hoerner, and H. V. Borst, Second Edition, published by Liselotte A. Hoerner, 1985, 7628 Staunton Place, N.Mex. 87120. Propeller disc contraction has not been completely addressed as suggested by the present inventor in his patent application Propeller Augmentation, No. 12 661 648, filed May 20, 2010. Airfoils have been designed to reduce trailing vortices, Chapter III, and Chapter XII FIG. 13. The present invention enhances the slipstream flow at little or no forward speed, and at greater speeds, increases the loading of the propeller disc per unit area, thus increasing the propeller capacity. Countless stationary air handling units, mobile units using air cooling, as well as airplanes, will benefit from this novel slipstream enhancing propeller apparatus.

SUMMARY OF THE INVENTION

The present invention relates to using the state of the art propeller containing a channel or trough fashioned spanwise on the back surface of the propeller, midway between the leading edge and the trailing edge, allowing a portion of the fluid or air encountered and raked off by the rotating propeller to accumulate the length of the channel or trough and forced via the channel or trough to the tip of the propeller blade at the trailing edge by centrifugal force. The exit trajectory of the fluid or air is parallel to the cambered face of the propeller and at approximately forty-five degrees to the longitudinal axis of the propeller. The velocity and capacity of the fluid or air varies directly as the speed of rotation.

It is an object of the invention to provide a method of propeller propulsion with less propeller slipstream disc contraction, thus producing more thrust and efficiency.

It is an object of the invention to provide a means for the exiting fluid or air from the trailing edge inducing flow over the cambered face of the propeller apparatus bootstrapping the capacity of the propeller by the jetting of the exiting fluid or air causing the propeller to turn more easily.

It is also another object of the invention to provide a method of propeller propulsion to improve the propeller propulsion efficiency.

The characteristics of the preferred device and its principle of operation will be more fully understood by reference to the following more detailed description and the attached drawings to which reference is made. The various components of the device, a propeller, are referred to in terms of reference numerals and letters, similar numbers being used in the different figures to designate components. In describing certain components, and features thereof, subscripts have been used with whole numbers for convenience to describe subcomponents of a different part.

The invention will now be described in connection with the accompanying drawings:

FIG. 1 is a perspective view 1 of a standard JZ Zinger 10/6 10 inch state of the art 1 pusher test propeller with the back surface 7, modified by a carved channel or trough 7, 9, the leading edge boundary of the said channel begins approximately 10 percent of the propeller chord 12 measured from the leading edge 5, and the channel bed is approximately 17 percent of the propeller mean chord to the to the leading edge of the channel bed 7, the width of which measures 20 percent of the mean propeller chord, and the depth of the channel bed 0.0714 times the mean propeller chord. The trailing edge of the channel is midway between the leading edge and trailing edge of the propeller back surface. An outline 6 shows the state of the art propeller back surface from the 10 percent distance position from the leading edge on a straight line directly to the trailing edge subtending the channel trailing edge boundary shown prior to carving the channel or trough. Rotation of the propeller 10 is shown. Fluid or air flow is shown 8 over the cambered face, and 14 over the propeller backside. The flow of air or fluid 13 that is raked off by the channel or trough is shown 7. The surface of the trailing edge boundary of the channel or trough 9 is at right angle to the flow 13.

FIG. 2 is a cross section view of the novel modified propeller 12 along lines 2-2 showing the direction of flow 14 of air of fluid passing over the modified propeller 7 across the cambered face 8, and the back surface 3 starting at the leading edge 5, and the trailing edge 4. The outline of the propeller back surface 6 prior to the channel being carved, is shown in relation to the modified novel propeller. The trailing edge boundary of the channel is midway between the leading edge and trailing edge of the propeller back surface and intersects the surface which outline 6 shows the state of the art propeller back surface prior to carving the channel. The flow of air or fluid 13 from the leading edge 5 over the back surface to the channel 7 wherein a portion of the air or fluid is raked off by trailing edge 9 boundary at a right angle to the flow and thereafter propelled to the propeller tip by centrifugal force.

FIG. 3 is a perspective end view of a test propeller showing fluid or air flow exiting 13 at less than a right angle 17 to the trailing edge from the tip of the propeller and parallel to the cambered face of the propeller 11, the flow vectors of the exiting fluid or air velocity of flow along the blade face 14, blade tip velocity 15, and resultant air velocity 16. Refer, e.g. to Steam, Air and Gas Power, Wm. Severns, and Howard E. Degler, John Wiley & Sons, 4^(th) Edition 1948, p. 218 , NY and London; and

FIG. 4 shows the performance curves of the control propeller and the novel modified slipstream enhanced propeller. The left Y axis is thrust in increments 250 grams, the right Y axis is propeller speed in increments of 1000 RPM. The X axis power input is in increments 1.0 amps.

EXAMPLES AND DEMONSTRATIONS

The following examples and demonstrations exemplify the novel channeled propeller of this invention; comparative data being presented to demonstrate the advantage in improved thrust and efficiency achieved pursuant to the practice of this invention.

Also, prior flight tests were made in a Wittman 125 horsepower retractable gear monoplane to obtain data of the magnitude of the slipstream disc contraction of a propeller driven airplane at airspeeds of 160 miles per hour. The airplane was equipped with a fixed pitch 68/75 propeller and further equipped with an airspeed indicator and pitot system mounted in the propeller slipstream taking airspeed readings at approximately 6 inches behind and in the slipstream of the propeller. The pitot tube of the airspeed indicator attached to the aircraft for this test was moved in increments of one inch starting at the tip of the propeller after each test flight which was noted during flights of 160 miles per hour. The slipstream contraction was measured to be approximately 6 inches for 68 inch diameter propeller and was found to be approximately 0.911, which is reasonable compared to the studies by S. F. Homer and H. N. Borst reference above. These results demonstrated a reduction of the slipstream disc contraction of the test aircraft and increased the flow of air at the propeller tips, and this indicates a viable subject for improvement in performance and efficiency as the following tests below demonstrate.

Tests of two 10 inch diameter two bladed 10/6 pusher propellers manufactured by JZ Zinger Company having a ratio of blade length to maximum blade chord of 5.71, were performed on a dynamometer. The first propeller tested, devoid of any modifications, was marked “Control Propeller”. The second test propeller, marked “Channelled Propeller”, back surface of which was modified by carving a channel or trough 7, 9, length of which is sixty-five percent of the blade lengthwise, at a depth of 0.0625 inches, and terminating a distance of five percent of the blade 3 length measured from the tip 5. A portion of the flow of air or fluid 13 passing over the channel or trough at right angle collects and flows 14 in the channel and exits the propeller near the tip at an angle of approximately forty-five degrees 17 to the longitudinal axis of the propeller. The direction of rotation 10 of both propellers were the same;

Demonstration One: The control propeller provided an average 969 grams thrust reading for an input of 4 amps at 7750 rpm.

Demonstration Two: The novel second modified channeled propeller provided an average 1070 grams thrust reading for an input of 4 amps at 7826 rpm.

There is a ten percent improvement of thrust of the control propeller by the novel channeled propeller.

Subsequent tests were made with the control propeller and novel modified propeller as demonstrated. The tests showed an increase in thrust readings, induced flow over the propeller apparatus camber 8, as well as having an increase in rpm. These tests as recorded in FIG. 4 of both propellers were made at inputs of 2.5 amps, 3.0 amps, 3.5 amps, and 4.0 amps. The results were plotted as shown. At 2.5 amps the modified novel channeled propeller showed a 10 percent increase in thrust compared to the test propeller devoid of the novel channel or trough. This increase continued throughout the rest of the plots.

It is apparent that various modifications and changes can be made without departing from the spirit and scope of the present invention. Changes in absolute dimensions of the parts, materials of construction used, and the like will be apparent to those skilled in the art. 

1. In apparatus characterized as a foil having a back surface extending from the leading edge to the trailing edge of said foil and an opposite camber surface extending from the leading edge to the trailing edge of said foil, between the opposite back surface and a fluid of which relative movement can occur, the improvement which comprises an area completely smooth on the cambered side, and the back surface smooth except for a channel or trough extending spanwise midway of the leading edge and the trailing edge subtended on a straight line to the trailing edge of said foil devoid of any indentations causing the fluid stream not to collect in the channel allowing the centrifugal force of the foil rotation to produce a flow to the foil tip to enhance the slipstream, improve performance and efficiency of the foil as contrasted with a foil otherwise similar except that it contains no channel, indentations, or projections in the area between the leading edge and the trailing edge.
 2. The apparatus of claim 1 wherein the foil is a hydrofoil and the fluid is water.
 3. The apparatus of claim 1 wherein the foil is an airfoil and the fluid is air.
 4. The apparatus of claim 3 wherein the airfoil is a propeller blade.
 5. The apparatus of claim 3 wherein the airfoil is a propeller with blades of which are provided with a single channel or trough spanwise on each blade back surface opposite the cambered surface spanwise midway between the leading edge and trailing edge of said propeller.
 6. The apparatus of claim 1 wherein the depth of the channel or trough ranging 0.0714 times the maximum chord of the foil from edge to edge.
 7. The apparatus of claim 1 wherein the foil which is provided with a channel or trough extending from a location wherein the inner ends of the blades are joined via a hub at the outer terminal ends of the blades.
 8. The apparatus of claim 1 wherein the channel or trough trailing subtended by a direct from the 10 percent position measured from the leading edge to the trailing edge boundary of the channel intersecting the back surface midway to the trailing edge, the said channel approximately 65 percent of the foil length and terminating approximately 5 percent of the foil length from the foil tip.
 9. The apparatus of claim 1 wherein a portion the flow of air or fluid passing at right angle to the leading edge of the foil raking off a portion of the flow which accumulates in the channel or trough and exits the said foil tip at the trailing edge parallel to the cambered face of the foil and at an angle measured from the tip of approximately 45 degrees to the longitudinal axis of the foil.
 10. The apparatus in claim 4, wherein the channel or trough at right angle to the air or fluid flow, rakes off a portion of the flow wherein accumulated during the rotation of the propeller apparatus the air is further propelled by centrifugal force via the said channel, reducing slipstream disc contraction at the propeller tips at zero or low forward speed, and at greater speeds, and inducing flow over the cambered face of the propeller apparatus increasing propulsion, plus bootstrapping by the jetting effect of the air exiting the trailing edge at the tip of the propeller apparatus. 